If the article is correct then, by using FSEvents, it will not work the Hard disk at all, only copying new files. It does not do a full read every hour, just looks at FSEvents table, so unless you creating tons and tons of files should be very economical.

Yeah, and that's like and antivirus program which the OS takes a hit from. If the article is correct and the browser cache is one of those places TimeMachine will ignore, then it shouldn't be too bad.

Two answers: (1) perhaps you could use iDisk as one while travelling... perhaps buying more .mac space would be worth it for road warriors!

and (2) There is a wonderful drive family from Western Digital called the "My Book" family. I bought a firewire 500GB from COSTCO for around $165. They are power efficient (shut down after xxx minutes) and very reliable.

The terabyte models should be out soon. I'll get one when I move to Leapard and still use backup to .mac and the 500G drives. Can't be too safe (as I just found out Monday!!!)

I don't think dot Mac can be a Time Machine destination due to response times being too slow. Though you are warned against doing so, you can use a partition on your internal hard disk (on the same physical drive being backed up) to let Time Machine do its thing. This protects you from user error ("Oops, I overwrote a file I needed") but it will not help at all if the drive itself fails. Large external drives are the way to go with Time Machine, IMHO. I'm especially eager to see what drive makers start offering.

Second, I also have a MyBook drive and offer a few warnings about it. First, make sure you get the ones which have USB2 and Firewire interfaces if you can swing the extra $30. Firewire is slightly faster than USB2 and if you ever want to use it as an emergency boot disk, you'll have a much easier time. Another thing, is that the packaging isn't always clear how many hard drives are inside. For example, their 1TB drive is really 2x500GB drives using a software RAID that requires Windows software to run. With all that said, it's a good drive for a reasonable price (500GB = $170; 750GB = $300 )

This is a good background article, but it misses the point of Time Machine, I think. Backing up files is old news, and I'm sure Time Machine does it as well as anyone. The real magic of Time Machine, though, is information retrieval. It's something that Shadow Copy and rsync can't hope to do.

In a traditional file backup solution, if you discover one missing record in your Address Book, you'd have to go get all your incremental backups, restore each file in turn, look for the record, and if you find it export it manually, then restore the current version and import it.

With Time Machine, you just search back through time using the same search field you do normally. It will go back in time and find the first instance of the search criteria and allow you to restore just that record to the present. THAT is revolutionary. The rest is just another implementation of an old concept.

So what happens if my whole system goes down - can I retrieve the situation using Time Machine - will it replace a bootable back-up system like Super Duper?

Yes it will. However, unlike SD!'s immediate recovery by simply booting up on the cloned Volume one has to restore the system from the complete TM backup. This is done by inserting the DVD Installer, selecting a new Volume to place the system on and then selecting the TM backup to restore. The Installer will then restore your system from the chosen TM backup. After the restore completes the Volume is perfectly bootable.

The beauty of the TM restore is that you can chose from time past what you want to restore. SD! will only restore what was last cloned.

The first TM backup size will be the aggregate sum of all the data not excluded from the TM backup selection. By default TM will ***exclude*** everything except your system's boot Volume. So if your system's boot Volume is say 100 GB then the size of the first TM backup will be 100 GB. However, be aware that there's some TM management overhead so it's likely the size will be a bit larger than the 100 GB.

The size of subsequent hourly backups will amount to the data churn done in the past hour. So, if say you add to a file that was originally 20 MB another 1 MB and create new data that amounts to say 10 MB then when the next TM snapshot backup executes the size of the snapshot backup would be 21 MB + 10 MB = 31 MB (plus some TM managemenmt overhead).

Does anyone have an idea of how big of a backup drive to get to use Time Machine? My internal drive is about 150GB.

Start off with a 500gig HD. If your budget is small get the least expensive one, otherwise get a combo one that provides USB 2.0, FW400 and FW800(if your Mac has FW800).

Another approach is to buy an enclosure and a retail HD to place into it. When this fills up with TM backups you can

1) Take out current HD from enclosure and insert a new one and safeguard the old. Then start a new full TM backup (this will be done automatically for you as TM will detect it's backup up to a different/new Volume)

2) Erase the current TM Volume/HD and start over again. Of course you will lose you TM backup history and if this doesn't bother you then nothing is really lost except time to srat another full TM backup.

Does this mean I am going to have to connect my external HD every hour to my macbook to make a backup? can I not make it backup just once a day or something?

Just connect the HD to your MB whenever you like. TM will notice it was attached and backup to it. If you shutdown the MB while TM backup is active you will be warned and given option to allow it to complete or you can quit and shutdown. When MB restarted after interrupting a TM backup the next TM backup will try and resume where it left off and complete the backup it started prior to you shutting down your MB.

If you look at the pictures, one of them shows the configuration pane for Time Machine, asking when to back up. The option listed is Backup at Midnight. I'm sure they will have a "Custom..." option. Don't underestimate Apple.

Here's what I wanted to know: I want to keep TWO backups. I've read that it's best to have one attached to your computer at all times as Time Machine will maintain, but another stored off-site in the event of a crash/robbery.

So, I wanted to know how/if I could accomplish this. Ideally, I would hook up one drive to Time machine, let it run for a half year, then swap out the other one, let it run for half a year and so on. But at that point, would I be confusing Time Machine, or losing data between backups or something else?

All of it is too complex. I really wanted to start doing backups as most of my valuable photos and projects have gone fully digital, but it seems not enough to me to simply have a single external drive hooked in to the computer sitting next to it. If there's a robbery or fire or something, it all goes away, including the backup.

It'd make my day to know that somehow all this logic could be easily maintained between two disks as an identical copy.

Any thoughts/assurances are welcome.

m.

This is a somewhat tough requirement to meet. What you could do is to use two HDs with one always offsite.

Use HD-1 for a week and then replace with HD-2 with HD-1 sent offsite.

After another week, replace HD-2 with HD-1 after erasing HD-1 and send HD-2 offsite.

Of course the week could be anytime frame you choose depending on how frequently you get robbed.

Remember that each time you switch in a different TM backup HD TM will want to perform a FULL backup of your data. This can be time consuming so do it just before bedtime. Also, when introducing a new HD to TM be sure to erase/re-formatt it first using Disk Utility.

This is a somewhat tough requirement to meet. What you could do is to use two HDs with one always offsite.

Use HD-1 for a week and then replace with HD-2 with HD-1 sent offsite.

After another week, replace HD-2 with HD-1 after erasing HD-1 and send HD-2 offsite.

Of course the week could be anytime frame you choose depending on how frequently you get robbed.

Remember that each time you switch in a different TM backup HD TM will want to perform a FULL backup of your data. This can be time consuming so do it just before bedtime. Also, when introducing a new HD to TM be sure to erase/re-formatt it first using Disk Utility.

I don't get robbed all that often, nor do people regularly firebomb my home, I'm happy to say. I just got antsy listening to stories of people who have lost years of their lives to stuff like that. I'd be pretty sad if I lost all of my data in a freak accident. Hence the need for off-site backups.

Thanks for your suggestion though. But swapping out every week would be tedious. I wonder if I could, as someone suggested earlier, make a copy of the Time Machine drive at semi-annual intervals. There's no reason that couldn't work, is there?

Or even better... if Time Machine can use multiple disks, then I could simply hook up one drive semi-annually, and the other just leave there. Perhaps it'll somehow know the difference. Hrm. I suppose I'll just need to wait for Leopard and try all these ideas out when I have the OS running.

So if I understand correctly, using Time Machine, disk space containing previous
versions of a file is not reused when new versions are created. It seems like
if you heavily edited many large files, your primary drive would run out of space much
sooner than it would without Time Machine, where space from obso versions
would be reused. Is this correct? Is it a big deal?

Upon further review, it is the backup drive and not the primary drive
which cannot reuse space. Maybe the 'backup storage time limits'
is for freeing up the BU drive.

Beautifully written article. And well worth reading it more than once.

Perhaps many here should visit Apple's site as well, i.e., at http://www.apple.com/macosx/leopard/...memachine.html. It may help answer some of the questions and perhaps negate some of the well-meaning but ignorant and/or ill-advised responses that have cropped up here as well.

Beautifully written article. And well worth reading it more than once.

Perhaps many here should visit Apple's site as well, i.e., at http://www.apple.com/macosx/leopard/...memachine.html. It may help answer some of the questions and perhaps negate some of the well-meaning but ignorant and/or ill-advised responses that have cropped up here as well.

I don't think dot Mac can be a Time Machine destination due to response times being too slow.

Why too slow?
Doing a backup just involves sending new files up to .Mac (a background task, but yeah it requires a good broadband connection). Looking into the past, afaik, is done either
1) on a per-folder basis - retrieving individual folder information is not bandwidth intensive
or
2) a spotlight search - and Leopard allows you to send a search request to another Mac, meaning .Mac would do a search itself and merely send the results to your machine.

I think .Mac backups have HUGE potential I don't know if Apple will enable it, but it seems to be the same technology as what will be used for local server backups anyway (just slower). It'd be great if Mozy offered the same thing.

So if you delete inode, associated with file data - in case of symlinks you loose both, your symlink, and the file (since symlink is simply a reference to the file), but in case of hard links the actual file data remains, since there's another inode (inode2) pointing to it.

Just connect the HD to your MB whenever you like. TM will notice it was attached and backup to it. If you shutdown the MB while TM backup is active you will be warned and given option to allow it to complete or you can quit and shutdown. When MB restarted after interrupting a TM backup the next TM backup will try and resume where it left off and complete the backup it started prior to you shutting down your MB.

oh ok, thanks for the info....but if you connect the external HD whenever you want does it still know what to backup???

Why too slow?
Doing a backup just involves sending new files up to .Mac (a background task, but yeah it requires a good broadband connection). Looking into the past, afaik, is done either
1) on a per-folder basis - retrieving individual folder information is not bandwidth intensive
or
2) a spotlight search - and Leopard allows you to send a search request to another Mac, meaning .Mac would do a search itself and merely send the results to your machine.

I think .Mac backups have HUGE potential I don't know if Apple will enable it, but it seems to be the same technology as what will be used for local server backups anyway (just slower). It'd be great if Mozy offered the same thing.

I'm currently using Superduper for my backup needs, doing the Copy Different option to an external drive, so apart from all the 'Point in time' niceness in Time Machine, and the hard linking stuff, the data I've got on my backup is sort of the same as what Time Machine would be keeping.

What I've noticed, and what I hope they've put in a mechanism for, is the problem of differential backups and podcasts. My external drive filled up, and I couldn't work out why until I found thousands and thousands of multi-meg files in iTunes under podcasts.

You never notice them on your own machine if you have the setting 'keep last 3' or similar, but the differential backup keeps everything, and eventually drowns in them.

Anyone else have a solution for this, or am I going to be impressed to find it's one of the standard Ignore folders in TIme Machine ?

Sure. But I assume it won't make 'temporary backups' while the external HD is offline, so of course you lose all hourly, daily or even weekly backups for the time you're away, right? Theoretically, this could be avoided (as hinted) by making all those backups to a temporary maybe hidden directory on your local HD, but I'm pretty sure TM won't do that.
Philotech

Sure. But I assume it won't make 'temporary backups' while the external HD is offline, so of course you loose all hourly, daily or even weekly backups for the time you're away, right? Theoretically, this could be avoided (as hinted) by making all those backups to a temporary maybe hidden directory on your local HD, but I'm pretty sure TM won't do that.
Philotech

TM backup will execute only if the configured backup Volume is mounted.

I have lots of questions on Time Machine.. Apple should make a FAQ or something because it's one of the features I think will cause more doubts!

-> Background: 99% of the time I use my Mac either at Work or at Home. At Home i have an Airdisk set up to automatically mount.

From what I understand, Time Machine will only work if the drive is mounted, otherwise TM won't perform the hourly backup. This means that if I chose to backup to Airdisk, when i'm at work no hourlies will be backed up.

a) Can I choose to both make a back up to my Aidisk AND an ENCRYPTED backup to a Windows samba share on a windows server at work?. Won't TM cofuse the two destinations?
I think this is weird since it might occur that a file is backed up to the server at work but not to my Airdisk and then If I try to recover it how could TM tell which one to look for? this confuses me a lot!

b) This is about the hourly/weekly backups.

For example:

Oct 12 7pm : newly created File A is backed up to TM
Oct 12 8pm : file A was previously (7.30pm) delted so it doesn't appear on this hourly backup.
Oct 13 12am: daily backup from Oct 12 is backed up to TM. It doesn't contain file A, but file A is backed up in hourly 7pm from oct 12.

Now... a few days later, it comes the time to delete hourly backups... how does TM manage to keep file A in the TM pool for me to recover at a later time?

@khyros re keeping of deleted files:
Wild speculative guess: Your file A will lost because the hard link feature does not provide a way to easily take care of it.
To keep it, it would require a consolidation of all 24 hourly backups. Then you'd have for each file 24 potential conflicts because you could have 24 versions. You'd say never mind just keep the latest, ie the 12am version. Fine that's what TM does right now. Unfortunately, the latest version of your file A is the deleted version, ie no file at all... But really that's no difference to a file that was created the day before and then amended a few times but finally deleted on that day: all changes that did not persist at 12am are lost, you only have the previous day's backup IF the file existed then already.
So you'd have to adjust the rule: for the 12am daily backup take the 12am snapshot of the file system UNLESS there were files existing before that have been deleted between 12am the previous day and 12am today. That would require full file checking and everything an ordinary backup program would do, and all the easiness and beauty of TM and hard links was gone. Not gonna happen. You need an ordinary backup programm for that and fire it off before deleting files.

The easier way to explain the difference between soft and hard links, in my opinion, is like this:

A file consists of an actual file data, and directory entry, known as inode, referring to the data.

A symbolic link is a file, referring the inode of the original file, so to access the file data a system has to travel through this path:

symlink => inode => file data.
...

Thanks a lot, that was much easier indeed. As much as I like the original article, the explanation of how links and everything work including the pictures is pretty much incomprehendable.
For consistency's sake, the depiction above should read (IMHO):
inode => symlink => inode => file data

A question for those who have tested it: how large should a typical Time Machine backup drive be? I understand that this will vary with our use etc., but let's assume that I have an iMac with a 320 GB disk, about 100 GB of it available. WHat size drive should I consider for backup?

Given that 500GB drives can be had now for under $100, get a 500GB & never think about it again (for a few years anyway - storage gets consumed, it's the nature of the thing)

My guess is no. You would probably need to reinstall the system and then retrieve your files from the backup..

I think the multiple meanings of "backup" are mixing us up: backing up files to a storage disk, from which they can be retrieved, is one sort of backup; maintaining a current bootable partition on a different drive from your main boot disk is another kind. neither replaces the other; they are complementary, and each is important.

As to whether one can restore a bootable partition from Time Machine, I suspect it does not, for the reason that it would involve "crossing the streams" Or, as an old Irishman once said, "when I drink whiskey, I drink whiskey, and when I drink water, I drink water."

I think the multiple meanings of "backup" are mixing us up: backing up files to a storage disk, from which they can be retrieved, is one sort of backup; maintaining a current bootable partition on a different drive from your main boot disk is another kind. neither replaces the other; they are complementary, and each is important.

As to whether one can restore a bootable partition from Time Machine, I suspect it does not, for the reason that it would involve "crossing the streams" Or, as an old Irishman once said, "when I drink whiskey, I drink whiskey, and when I drink water, I drink water."

TM will restore a complete system backup and it will be bootable afterwards. Pop in the DVD Installer disc, select the Volume you wish to restore to, select the complete TM backup you want to restore from, wait for it to complete the restore operation and then you will have a bootable system once again. Works just fine, easy to do and without any real fuss.

This is a good background article, but it misses the point of Time Machine, I think. Backing up files is old news, and I'm sure Time Machine does it as well as anyone. The real magic of Time Machine, though, is information retrieval. It's something that Shadow Copy and rsync can't hope to do.

In a traditional file backup solution, if you discover one missing record in your Address Book, you'd have to go get all your incremental backups, restore each file in turn, look for the record, and if you find it export it manually, then restore the current version and import it.

With Time Machine, you just search back through time using the same search field you do normally. It will go back in time and find the first instance of the search criteria and allow you to restore just that record to the present. THAT is revolutionary. The rest is just another implementation of an old concept.

The Shadow Copy service in Vista can do just that. In fact, Sharepoint and Exchange implements this feature extremely well. I can pull back any one piece of data (a calendar event, email, contact etc.) without restoring or exporting the entire record.

Even with Previous Docs you can open up an old folder and just re-instate one file out of that shadow copied folder. The API lets you go even further detail by allowing (or disallowing) certian items to be restored together AND NOT separately. For instance, if you have a bank record of a deposit into one account (item 1) from another account ( item 2) you can make it so it is impossible to reverse item one without reversing item 2 at the same time. That's a simplistic example but it shows the power of A.C.I.D. transactions in Vista/NTFS6.

Quote:

The data backup features related to Shadow Copy are only useful if a Windows machine is running in an environment with a server backing them up. Shadow Copy is not in itself a backup system, although it can present a listing of duplicated files that were captured by the shadow copy service. Without a dedicated backup system, Previous Versions only shows local shadows of a file. It does not copy files to an external disk for safekeeping, and its shadow copies can't be browsed through by the user in the file system by date or by query. Shadow Copy is certainly not an easy to use consumer backup solution (nor is intended to be), which is what Time Machine expressly is.

That's incorrect. Vista comes with a backup program (that uses Shadow Copy) that can copy incremental backups to external media and hard drives as well as network connected drives. Previous Docs also allows one to search and browse through backups using Windows Explorer by date, time, and numerous other criteria. In fact, if you open a folder from the previous docs window you will see that the address bar shows you the name, date, and time of the folder snapshot in naturall language and that you can do a natural language search over that data or use the breadcrumb bar to see other times and snapshots registered in the file system.

That's incorrect. Vista comes with a backup program (that uses Shadow Copy) that can copy incremental backups to external media and hard drives as well as network connected drives. Previous Docs also allows one to search and browse through backups using Windows Explorer by date, time, and numerous other criteria. In fact, if you open a folder from the previous docs window you will see that the address bar shows you the name, date, and time of the folder snapshot in naturall language and that you can do a natural language search over that data or use the breadcrumb bar to see other times and snapshots registered in the file system.

Be careful when pointing out inaccurate statements about Windows here, because you might get told something like "If you know so much about Windows, then why don't you just buy a PC?". If the feature does not work exactly like the Mac, then it doesn't exist.

This is a good background article, but it misses the point of Time Machine, I think. Backing up files is old news, and I'm sure Time Machine does it as well as anyone. The real magic of Time Machine, though, is information retrieval. It's something that Shadow Copy and rsync can't hope to do.

And that is where you need to be careful. Other than the amazing visual experience offered by Time Machine and the integration with individual applications, rsync is *very* much capable of achieving *exactly* the same backup strategy. Tiger already supports hard links as discussed in the article and rsync supports syncing content using hard links to avoid storing redundant copies of the same file. Sure, it's not going to be as user friendly, but it would actually work.

Quote:

In a traditional file backup solution, if you discover one missing record in your Address Book, you'd have to go get all your incremental backups, restore each file in turn, look for the record, and if you find it export it manually, then restore the current version and import it.

With Time Machine, you just search back through time using the same search field you do normally. It will go back in time and find the first instance of the search criteria and allow you to restore just that record to the present. THAT is revolutionary. The rest is just another implementation of an old concept.

With rsync and hard links there would be no "restore" as such, you'd just change to a folder on your backup drive that corresponds to a backup date. That folder would appear as a full backup.

I agree that rsync isn't as good an option as Time Machine appears to be from a usability point of view - but lets not forget that it is actually capable of achieving a very similar result in terms of file storage and retrieval.